Effects of Long-term Intensive Exercise on the Expression of miR-155 and miR-146a in Ventricles

Objective:To study the effects of long-term intensive exercise on the expression of miR-155 and miR-146 a in ventricular, and to discuss the role of miR-155 and miR-146 a in exercise induced myocardial fibrosis and inflammation. Methods:48 male SD rats were divided into sedentary (Sed) group and intensive exercise (IE) group randomly, and every group has three time points (eight-week, twelve-week and sixteen-week) , thus there are 6 groups (n=8) . Rats in sedentary groups are free activities. Rats in IE group run on treadmill at the speed of 28 m/min, 10° slope for 8 weeks, twelve weeks or 16 weeks (1 hour per day, 5days per week) . After the last training, all rats were sacrificed, separate left and right ventricular. Expression level of miR-155, miR-146 a and their downstream target gene SOCS1, IRAK1 m RNA was measured by RT-PCR. Results:Long-term intensive exercise increasing miR-155 expression level in right ventricular, but without changes in left ventricular. Expression level of miR-146 a in right ventricular was increased after sixteen-week intensive exercise, but no alteration in left ventricular. After long-term intensive exercise, SOCS1 m RNA expression level without changes both in left and right ventricular. The expression level of IRAK1 m RNA in right ventricular was increased after long-term intensive exercise, but without changes in left ventricular. Conclusion:Long-term intensive exercise promotes inflammation via up-regulate miR-155, which is the potential mechanism of exercise-induced myocardial fibrosis.